This invention relates to wheelchairs and, more particularly, to hand rims for hand-propelled wheelchairs.
Many conventional hand-propelled wheelchairs are equipped with tubular steel hand rims with a circular cross-section. Each hand rim is usually mounted outboard of its respective wheel by connectors, such as spacers (standoffs), to provide a clearance between the hand rim and wheel. Some lightweight wheelchairs are equipped with integral hand rim and wheel rim assemblies. A combined hand rim and wheel rim for a wheelchair can also be formed from a single extruded section.
Wheelchair hand rims enable the wheelchair user to control the wheelchair's movement, such as acceleration, turning and braking. While generally suitable for their intended purpose of propelling and maneuvering the wheelchair, conventional wheelchair hand rims have numerous disadvantages. For example, the smooth metal surfaces of wheelchair hand rim tubing sections provide only limited gripping surfaces for the user. Furthermore, when the weather is humid, damp or rainy, or if the user's hands are perspiring, the wheelchair hand rims can become slippery. Often, when the user attempts to propel the chair in difficult situations, as when going up ramps, traveling on wet pavement, moving on soft carpets, traversing dirt or gravel areas, grass or other rough terrain, the user often experiences difficulty and must resort to such tactics as placing their hands over both tires and hand rims to exert sufficient torque. Moreover many users push forward with the help of the tire to increase friction. Dirt and debris on the tires, and glass, stones or metal objects stuck in the tire can dirty and even injure the user's hands. The standard hand rims also limits the ability of the user to properly and safely control the brake the wheelchair while descending a ramp. Also, a considerable amount of the user's effort is expended in gripping the slippery metal hand rims rather than in applying torque to propel the wheelchair.
In the marketplace today there are coated hand rims for wheelchairs and non-coated hand rims for wheelchairs. Coated hand rims can be used by people with reduced hand strength or function. Coated hand rims offer somewhat higher friction. There are different types of coatings available in the market place including hard coatings, such as hard vinyl and hard urethane, and soft coatings, such as soft vinyl and molded isobutyl foam rubber. However, the disadvantages of coated hand rims are that when braking the high friction coated hand rims cause the hands to get very hot which can bum or otherwise injure the user's hands. Furthermore, most conventional coated hand rims are not very durable, and often become unusable in less then six months. Hard coatings can be easily chipped away with use, creating sharp edges which can cut the user's hand. Soft coatings, such as soft vinyl and isobutyl foam, do not have sharp edges, but have a much shorter life. The non-coated hand rims are used primarily by people with full strength and function in their hands. For most users with full hand strength and function, the disadvantages outweigh the benefits and most buy non-coated hand rims. All users could however, benefit from additional traction when accelerating.
In recent years wheelchair sports have become increasingly popular, and have prompted changes directed toward making wheelchairs more easily and efficiently maneuverable. Sport wheelchairs are often equipped with hand rims formed from a slightly larger diameter tubing which improves the grip to some extent. The grip may be further improved by providing a soft vinyl coating on the hand rim, but this has the disadvantage of considerably diminishing the durability of the hand rim.
A different set of problems may be presented for paraplegics, quadrapalegics, users with multiple sclerosis and others having limited grip strength. Some conventional hand rims for such users utilizes a circular ring similar to regular hand rims, but having plurality of radially or axially projecting handles or push rods which the user may push with their palm without having to grip. These so-called projection hand rims are useful when required, but are heavy and relatively expensive. Moreover, they are extremely awkward and unsuitable for general use. The main problem with projection hand rims with push rods is difficulty in braking. Also, the push rods can become caught up on draperies, furniture, and the like. Some wheelchairs utilize a system in which push rods are partially retracted towards the bottom of their travel, thereby at least partially obviating this problem. However, this result is achieved at the expense of complexity.
It is, therefore, desirable to provide an improved wheelchair hand rim which overcomes most, if not all, of the preceding problems.